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Summary: This document explains mailbox permissions in Exchange Online, covering read, send-as, and send-on-behalf permissions. It provides step-by-step instructions for assigning these permissions through Microsoft 365 Admin Center and Windows PowerShell and introduces Kernel Office 365 migration software for seamless migrations.

While Exchange mailboxes typically have permissions associated with a single account, various accounts can possess diverse permissions tailored to their specific roles. When a mailbox user departs from the organization, it doesn’t imply that their data becomes obsolete. The administrator can modify mailbox permissions and grant access to other users through various means. For instance, mailbox permissions are essential for enabling one user to send emails on behalf of another employee, necessitating the assignment of appropriate permissions.

Mailbox Permissions in Exchange Online

You have the option to provide another user with read and write access to a mailbox through mailbox permissions. This grants the user the capability to read emails stored in the mailbox, send emails on behalf of another user, and send emails that appear to originate from that mailbox.
So, there are three types of permissions-

  • Read another user’s emails.
  • Send emails from another user’s account.
  • Send emails on behalf of another user’s mailbox account.

All three permissions can be assigned to the active users in the organization that have Exchange Online accounts, and there are two methods to assign such permissions-

  • Using Microsoft 365 Admin Center.
  • Using Windows PowerShell.
Assign Mailbox Permissions in Exchange Online using Microsoft 365 Admin Center.

In the Admin Center, you can set the permissions on specific mailboxes individually. Follow the steps-

  1. Login to Microsoft Admin Center and click on Admin. Then, go to the Active users list in the Users section.Users section
  2. Double-click on the account, and its settings will open. Go to its Mail category, and there will be mailbox permissions. All three permissions will be there, and you can click on one. Let’s start with ‘Read and manage permissions.’manage permissions
  3. Click on the + Add permissions option.Add permissions
  4. Select the mailboxes that will get the chosen permissions. Click the Add button.Click the Add button
  5. Changes are saved. The selected mailboxes can read emails from the user mailbox and run management functions like adding and removing content.adding and removing content.
  6. Similarly, you can apply the ‘send as’ permissions, and the users can send emails as the original user account.send as permissions
  7. The ‘Send of behalf’ permission helps the user to send emails with both the original account and mailbox name. The emails will show that they were sent on behalf of the original account.Send of behalf
Assign Mailbox Permissions in Exchange Online using Windows PowerShell

You can use PowerShell to assign mailbox permissions easily.

  1. Connect the Windows PowerShell with Exchange Online with the help of the following link-
  2. Run the new cmdlet to assign full permissions to another mailbox-
  3. Add-MailboxPermission -Identity “John Price” -User Patrick -AccessRights FullAccess -InheritanceType All

    The example assigns the complete permissions of John Price’s mailbox to Patrick. both methods would help you in understanding different admin roles in Office 365 and how it affect the mailbox usage and its function.


Numerous users who were previously utilizing Exchange on-premises have transitioned to Exchange Online in the cloud, specifically within Office 365. Nonetheless, this migration is not a straightforward process, especially when considering a manual migration of the entire Exchange infrastructure to Office 365.

Fortunately, the Kernel Office 365 migration software is available to assist you with this transition. It is capable of seamlessly accessing all on-premises Exchange mailboxes and facilitating their migration to Exchange Online accounts. This software streamlines the entire migration process, ensuring the seamless transfer of all mailboxes and associated data.

Kernel Office 365 migration